The present invention relates to an apparatus for the perforation of the femur and the tibia in surgical operations, particularly for installing front and rear crossed prosthetic ligaments in the articulation of the knee.
In a recent implantological method the ligaments of the knee can be replaced with bands or strands of particular biocompatible materials: such bands are inserted in two corresponding bores which must have their inlets substantially on the front faces of the tibia and of the femur and their outlets in the rear regions respectively of the tibial plate and of the condyloid cavity of the femur. The ends of the bands, conveniently provided with slots or the like, are connected at the bores inlets by screws which are intended to be definitely removed, after the fibers have biologically associated with the bone.
It has been observed that a long time is required by this surgery for the installation of the prosthetic ligaments because of the difficulties encountered in providing the bores in the bones. For a good operation of the knee joint, in fact, bore outlets must be located in extremely precise positions (surgical points), defined by the surgeon, which, however, are located behind the knee on the opposite side with respect to that on which the patient is operated.
Currently, a first small test bore is drilled using a small bit with great care and caution, checking the alignment as the bit drills through the bone; the surgeon then manually checks the location of the bore outlet by passing a finger behind the articulation; if the bore outlet is considered to be acceptably located, the bore is progressively widened with increasingly larger-diameter bits with the aid of steel guide wires inserted in the bore; if instead the bore outlet is in a position which is considered unacceptable, another bore is drilled.
It is obvious that, also in view of the fact that the bore is inclined with respect to the surface of the bone, there are great difficulties in drilling the bores correctly.
Another great difficulty is due to the fact that in the bore outlet regions there are vessels and tissues which must absolutely not be damaged by the drill bit: finally the bore outlets must be bevelled to avoid stresses which may damage the fibers of the band.